Manufacturing of semiconductor devices commonly requires deposition of electrically conductive materials on semiconductor wafers. The conductive material, such as copper, is often deposited by electroplating onto a seed layer of metal deposited onto the wafer surface by a physical vapor deposition (PVD) or chemical vapor deposition (CVD) method. Electroplating is a method of choice for depositing metal into the vias and trenches of the wafer during damascene and dual damascene processing. To meet the demands of modern semiconductor processing, the electrically conductive material deposited on the surface of a semiconductor wafer needs to have the lowest possible defect density.
Damascene processing is a method for forming interconnections on integrated circuits (ICs). It is especially suitable for manufacturing integrated circuits, which employ copper as a conductive material. Damascene processing involves formation of inlaid metal lines in trenches and vias formed in a dielectric layer (inter-metal dielectric). In a typical damascene process, a pattern of trenches and vias is etched in the dielectric layer of a semiconductor wafer substrate. Typically, a thin layer of an adherent metal diffusion-barrier film such as tantalum, tantalum nitride, or a TaN/Ta bilayer is then deposited onto the wafer surface by a PVD method, followed by deposition of electroplate-able metal seed layer (e.g., copper, nickel, cobalt, ruthenium, etc.) on top of the diffusion-barrier layer. The trenches and vias are then electrofilled with copper, and the surface of the wafer is planarized.